Britain called for closed-door consultations of the UN Security Council to be held later Friday on Somalia's decision.

Haysom, a South African lawyer and experienced diplomat, was told to leave Somalia on Tuesday after he questioned the government's decision to arrest an al-Shabaab defector who was running in elections.

Muktar Robow, who defected from Al-Shabaab in 2017, was arrested last month and flown to the capital Mogadishu after announcing his bid for the state presidency in South West State.

The arrest sparked protests in the southwestern town of Baidoa on December 13-15 that were violently suppressed by Somalia's security forces, leaving at least 15 dead.

In a letter sent to the government, Haysom requested an investigation of the protest violence and information on the legal basis for arresting Robow.

At a Security Council meeting on Thursday, Somalia's Ambassador Abukar Dahir Osman said the United Nations should not interfere in his country's national affairs.

The ambassador said former Shabaab militants "cannot assume leadership positions without going through stringent established rehabilitation programs," adding that a terrorist should not be allowed to rebrand himself as an "ice cream salesperson."

Haysom warned of a risk of conflict during elections in Somalia's federal states due to tensions with the central authorities.

The arrest of Robow could discourage other Shabaab militants "who may be considering exchanging violence for a political path," said Haysom.

The UN mission in Somalia is tasked with supporting peace efforts and the strengthening of government institutions in the Horn of Africa nation, which were ruined by decades of civil war.